Despite extensive research, the etiology of a substantial proportion of the leukemias remains unexplained. Studies suggest, however, that a significant proportion of the leukemias, particularly acute nonlymphocytic leukemia (ANLL) might be due to environmental or occupational exposures. Immunologic and cytogenetic advances suggest that ANLL and acute lymphocytic leukemia (ALL) are each comprised of many different diseases with similar appearance, and other studies suggest that risk factor identification might depend upon identification of precise subgroups of either disease. A study being done in the epidemiology branch is designed to address the potential for enhanced risk factor detection in well-characterized subgroups of leukemia patients. The study was motivated, in part, by clinical reports suggesting that leukemia patients with specific chromosome changes in bone marrow were more likely than other leukemia patients to have had prior chemotherapy or occupational exposure to chemicals. Using a case-control design, as many as 550 adults with ANLL and 150 adults with ALL who enroll for treatment in first line treatment protocols sponsored by a cooperative cancer treatment group will be studied to determine leukemia risk associated with a variety of environmental and occupational exposures. Patients with leukemia are identified at diagnosis and interviewed by telephone while they are still hospitalized regarding exposure to solvents and chemicals, active and passive smoking, use of hair dyes, irradiation, and family history of certain diseases. Healthy comparison subjects chosen by random telephone screening are also interviewed. Cytogenetic studies being done by the cooperative group will be used to classify patients according to the presence or absence of particular chromosomal abnormalities, and risk factors for specific subgroups of patients will be evaluated. Risk factors will also be correlated with other clinical and laboratory parameters such as FAB classification and immunologic phenotype.